Conservative justice spokesman Bill Aitken said that Abdelbaset Ali Mohmed Al Megrahi "now surpasses the record for the longest amount of time a convicted murderer has been free after being granted compassionate release".

The Libyan, who has terminal prostate cancer, was controversially released from jail on August 20 last year.

Details published on the Scottish Government website showed 38 prisoners have been granted compassionate release since 1993.

Megrahi has now lived longer than the other convicted murderers who have been freed over this period - prompting fresh calls for Justice Secretary Kenny MacAskill to release medical reports on the bomber.

At the same time it was reported Megrahi has been working on a television documentary, which could be released later this year.

Mr Aitken said: "Since the Lockerbie bomber was released, he has enjoyed a life of luxury, celebrated his birthday and now surpasses the record for the longest amount of time a convicted murderer has been free after being granted compassionate release.

"It is now nine months since Britain's worst mass murderer returned to Tripoli to a hero's welcome. The SNP Government has yet to come clean and produce the evidence that set him free.

"The public has a right to see that evidence. He is supposed to be getting regular medical checks and monitoring - these must be made public as well."